Compression of Aggregates of Acid-Leached Coal Gangues: Implications for Coal Mine Backfill

Abstract

The compression mechanical properties of coal gangues subjected to acidic immersion were examined using a cylinder and a YAS-500 electrohydraulic servotesting system in order to investigate the effects of pH and particle size on its compaction stress-strain and stress-compaction relationships. The evolutionary trends of the leaching solution’s pH at various immersion times during the coal gangue corrosion process were analyzed. Then, inductively coupled plasma optical emission spectroscopy (ICP-OES) was performed on the leaching solutions to determine their chemical compositions and concentrations. An X-ray diffractometer (XRD) and X-ray fluorescence (XRF) spectroscopy also performed qualitative and quantitative analyses of the coal gangues samples. The mechanisms of hydrochemical corrosion in coal gangues were ultimately elucidated by analyzing these results, taking into consideration the chemical reactions of the acidic solutions and coal gangues. The results indicate that hydrochemical damage in coal gangues is more sensitive to small particle size and stronger acidity. The compressive mechanical properties of coal gangues that had been immersed demonstrated that their bearing capacity decreased as the particle sizes decreased and acidity increased. It was also established that acid leaching changes the mineral composition, particles, and pores of coal gangues, thus degrading their compressive mechanical properties.